Large area dissolvable template lithography

ABSTRACT

A method and apparatus for patterning a substrate are provided. A template is formed by applying a precursor material to a patterned master substrate and curing or solidifying the precursor material. The template is detached from the master substrate using a carrier having a curved surface. The template is coated with a patterning material, and is then detached from the carrier and applied to the substrate to be patterned. The template is then dissolved without affecting the patterning material, and the patterning material may thereafter be finished to develop the pattern. In an alternate embodiment, the patterning material may be applied to the substrate and then imprinted using the template.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 61/159,752, filed Mar. 12, 2009, which is herein incorporatedby reference.

FIELD

Embodiments of the invention relate to methods and apparatus forpatterning substrates. More specifically, embodiments of the inventionrelate to pattern transfer by physical means for lithography processes.

BACKGROUND

The semiconductor processing industry relies on lithography to createpatterns on substrates. As the density of features on substratesincreases with the progress of Moore's Law, lithographic methods havebeen challenged to produce repeatable patterns with smaller featuresover large areas with high throughput.

Standard lithographic methods utilize a mask to cover portions of thesubstrate to be protected from patterning radiation. In standardphotolithography, a light-sensitive photoresist is applied uniformlyover the substrate and then exposed to radiation through apattern-bearing reticle. The resolution of this process is limited bythe wavelength of light used, which is typically 248 nm or 193 nm inconventional UV processes. A historical advantage of manyphotolithography processes was that an entire substrate could be exposedat once, improving throughput. The key disadvantage today is thatcurrent photolithography processes struggle to resolve features smallerthan about 50 nm in size. For example, some current photolithographyprocesses may create features smaller than about 50 nm in size, but onlyover a small field of a substrate. Finer resolution over a large fieldwill be needed for future fabrication at dimensions smaller than 50 nm.

Electron beam, or e-beam, lithography is capable of very fineresolution. A substrate is similarly covered with an e-beam sensitivephotoresist and then exposed to e-beam radiation. A disadvantage of thistechnique is that the exposure must be accomplished by scanning thesubstrate with a beam of electrons. Each spot on the substrate must belighted with the beam. This takes time, reduces throughput considerably,and introduces problems of uniformity. Hybrid processes involving UVlithography for larger features followed by e-beam lithography forsmaller features may improve the result, but such processes areprohibitively expensive, and only effective when there are significantfeatures of larger dimension. As devices become smaller, features withdimension large enough to be resolved by UV lithography becomeincreasingly rare.

In the manufacture of flat panel displays, for example, large substratesup to and exceeding 1220×1400 mm are currently subjected to opticallithography processes such as proximity printing, step and repeatlithography, multi-lens scanning, and mirror projection. Proximityprinting, multi-lens scanning, and mirror projection typically use verylarge area masks comparable in size to the substrates being processed.These masks may cost up to $1 million each. Moreover, as the masks growlarger, they must be made thicker and heavier to survive handling duringthe process, and to minimize physical distortion of the mask. In somecases, such physical distortion can only be overcome by usingcomplicated and expensive optics.

Pattern transfer by physical contact is a promising technique forpatterning substrates, including large area substrates, at dimensionsless than 50 nm and extending up through many tens of microns. A patternis developed in a template, and then physically applied to thesubstrate. The template serves as a pattern transfer medium for thepatterning process. Efficient, high-throughput methods are still needed,however, to fully implement physical contact lithography for massproduction of next generation devices.

SUMMARY

Embodiments of the invention provide an apparatus for patterning asubstrate, comprising a master substrate, a substrate support, and atemplate carrier movable between the master substrate and the substratesupport, wherein the template carrier comprises a curved templatecontact surface having a width and a radius of curvature, wherein aratio of the radius of curvature to the width of the contact surface isat least about 10:1.

Other embodiments provide a method of patterning a substrate, comprisingforming a template having a pattern to be applied to the substrate,attaching the template to a plate-like carrier having a curved surface,coating the template with a patterning material, applying the templatecoated with the patterning material to the substrate and detaching itfrom the carrier, dissolving the template, uniformly removing a portionof the patterning material to expose portions of the underlyingsubstrate, treating the exposed portions of the underlying substrate tochange either the properties or the topography of the substrate, andremoving the patterning material.

Other embodiments provide a processing system for patterning substrates,comprising a first plurality of master substrates, each master substratecontaining a pattern to be transferred to one or more final substrates,a second plurality of carriers for moving flexible templates formed fromthe master substrates, each carrier having a curved template contactsurface, and a third plurality of pattern transfer stations, eachstation having a substrate support, wherein each of the plurality ofcarriers moves between one or more master substrates and one or morepattern transfer stations.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A-1H are side views of substrates and apparatus engaged in amethod according to one embodiment.

FIGS. 2A-2C are detail views of an apparatus performing a methodaccording to one embodiment.

FIG. 3A is a side view of a processing system according to oneembodiment.

FIG. 3B is a top view of the processing system of FIG. 3A.

FIG. 4A is a side view of an apparatus according to one embodiment.

FIG. 4B is a detail side view of an apparatus according to anotherembodiment.

FIG. 4C is a detail side view of an apparatus according to anotherembodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Embodiments of the invention generally provide methods and apparatus forpatterning substrates. Features having dimension from tens of microns toless than about 100 nm, such as less than about 50 nm, or less thanabout 25 nm, for example between about 1 nm and about 20 nm, or betweenabout 1 nm and about 10 nm, can be resolved using embodiments describedherein. In most embodiments, a pattern is transferred to the substrateusing a template as the pattern transfer medium. The template willusually be coated with a patterning material and then physically appliedto the substrate such that the patterning material contacts thesubstrate. The template is then dissolved to leave the patterningmaterial, which is then used to create the pattern on the substrate.

In one embodiment, a master substrate is created by forming a pattern ina rigid substrate using a process capable of very fine resolution. Apattern having features smaller than about 50 nm, such as smaller thanabout 25 nm, or smaller than about 15 nm, for example between about 1 nmand about 20 nm, or between about 1 nm and about 10 nm, may be createdin a glass or metal substrate by exposure to an e-beam lithographyprocess. A patterning material sensitive to e-beam treatment is appliedto the master substrate in a layer and patterned with an electron beam.The electron beam is capable of defining features having dimension lessthan 50 nm, such as less than 25 nm, such as about 10 nm or less. Theelectron beam changes the patterning material such that portions thereofexposed to the beam may be removed, exposing the substrate below. Thesubstrate may then be etched to transfer the pattern to the substrate,or alternately substrate material may be deposited over the exposedportions of the substrate. The etching may be accomplished using anetchant, such as a wet or dry etchant, selected based on the chemistryof the substrate. In most embodiments, a durable rigid master substratethat may be used to create many templates is preferred. FIG. 1A is aschematic side view of a master substrate 102 that has a pattern formedon one surface. In some alternate embodiments, a pattern having featuressmaller than about 50 nm may be created in a substrate using otherprocesses such as some highly localized photolithography processes.

A template is formed having the pattern of the master substrate. Atemplate material is applied to the patterned surface of the mastersubstrate in a way that the interface between the template material andthe master substrate reflects the pattern of the master substrate, butthe surface of the template material opposite the patterned interfacesurface is substantially smooth and flat. The template material maygenerally be applied as a liquid or vapor using a process suited forapplying a liquid or vapor layer to a substrate, and is generally amaterial that may cure, dry, or condense into a flexible solid material.In some embodiments the template material may be a liquid that isapplied to the master substrate by spin coating, die coating, slotcoating, or extrusion coating. In yet another embodiment, the templatematerial may be deposited as a vapor by physical vapor deposition,chemical vapor deposition, epitaxy, or atomic layer deposition, any ofwhich may be plasma-enhanced. FIG. 1B is a side view illustrating themaster substrate 102 with the template 106 disposed thereon.

The template material is generally cured, dried, or treated to form aflexible solid. In some embodiments, the template material may be apolymer that is applied as a liquid and solidifies by curing or drying.For example, polyvinyl alcohol (PVA) may be applied to the mastersubstrate as a water solution and allowed to dry, or encouraged to dryby heating gently. PVA becomes a strong, flexible solid upon drying. PVAmay also be made by hydrolysis of polyvinyl acetate. In otherembodiments, the template material may be an elastomeric material thatmay be applied as a liquid or emulsion and dried or cured by heattreatment, or by exposure to light or other radiation. In general,suitable template materials will be removable by a process that does notharm underlying materials. For example, if the template is used to applya patterning material, a template material is generally chosen that hasdifferent solubility or reactivity than the patterning material. A PVAtemplate may be used to apply a resist that is not water soluble, or anelastomeric template may be used to apply a resist that is not solublein a hydrocarbon.

When the template has solidified, it is removed from the mastersubstrate so it can be used for patterning. A carrier is used todisengage the template from the master substrate in a way that imposesonly controlled stresses on the template. The controlled stressesdisengage the template such that compensation can be made for anyresulting distortion of the pattern expressed in the template. In oneembodiment, the carrier is a plate-like article similar in size to themaster substrate and the template, with at least one surface having aslight curvature. The curvature may have a single axis, or multipleaxes, which may be parallel or intersecting. Examples of curvatureinclude spherical, cylindrical, ellipso-cylindrical, ellipso-spherical,ellipsoid, spheroid, and the like.

In general, the curvature will be small. In many cases, the curvedsurface is convex. For example, in one embodiment, if a carrier with acurved surface rests on a flat support surface with the center of thecarrier contacting the support surface, the edges of the carrier mayform a gap with the support surface that is no more than about 1 mm inwidth. In some embodiments, the carrier surface will have a radius ofcurvature that is at least 10 times one dimension of the carrier, suchas a major dimension of the carrier. For example, in one embodiment, ifthe carrier has the shape of a square with each side being 3 m inlength, the radius of curvature of a cylindrical curved surface will beat least about 30 m. In embodiments with more than one radius ofcurvature, at least one such radius will be at least 10 times onedimension of the carrier, such as a major dimension of the carrier. Inother embodiments, the ratio of a radius of curvature to a surfacedimension of the carrier may be at least about 100:1, such as at least500:1, at least about 1000:1, at least about 1,500:1, and/or at leastabout 2,000:1. In other embodiments, the ratio of a radius of curvatureto a surface dimension may be between about 10:1 and about 2,000:1, suchas between about 10:1 and about 100:1, or between about 10:1 and about1,000:1, or between about 100:1 and about 1,000:1.

In embodiments wherein the curvature has more than one axis, the radiusof curvature around each axis may be the same as, or different from,that around other axes. In some embodiments, the curvature may have aconical, spherical, ellipsoidal, or cylindrical shape, or a combinationthereof. Moreover, the curvature around different axes may havedifferent senses or directions. For example, the curvature around oneaxis may be convex while the curvature around another axis is flat,convex, or concave. The opposite side of the carrier, which does notcontact the template material, may have a flat or curved shape as well,and may be convex or concave with a conical, spherical, or ellipsoidalshape. In embodiments having more than one axis of curvature, the axesof curvature may be parallel or intersecting.

FIG. 1C is a side view illustrating the master substrate 102 withtemplate 106 formed thereon. A carrier 108 is positioned to detach thetemplate 106 from the master substrate 102. The carrier 108 hascharacteristics substantially similar to those described above, with thesurface contacting the template having a slight curvature. The curvatureenables the carrier 108 to detach the template 106 from the mastersubstrate 102 by attaching to the template 106 at a first edge 116,rocking across the template 106 so that the carrier 108 contacts thetemplate 106 at a second edge 118 of the template 106, and attaching tothe template 106 at the second edge 118. FIG. 1D is a side viewillustrating the carrier 108 with the template 106 attached at the firstedge 116 and contacting the carrier 108 at the second edge 118. Thecurved surface of the carrier 108, coupled with the rocking motion ofthe carrier 108 with the template 106 attached at the first edge 116,detaches the template 106 from the master substrate 102 at the firstedge 116 and for some distance along the length of the template 106. Asthe carrier 108 rocks across the master substrate 102, the template 106simultaneously adheres to the carrier and detaches from the mastersubstrate at the moving contact point of the carrier and the template.This method of detaching the template 106 from the master substrate 102results in forces being transmitted to the template 106 that minimizedistortion of the template pattern and allow compensation for any suchdistortions. Wishing not to be bound by theory, it is believed that theforces transmitted to the template by this detaching method aresubstantially unidimensional and perpendicular to the flat smoothsurface of the template 106. This unidimensional force minimizesstresses that tend to distort the pattern formed in the template 106 asit is peeled away from the master substrate 102, and offsets for anysuch distortions are readily identifiable.

The template 106, attached to the carrier 108, is positioned to receivea coating of a patterning material. The patterning material may, in someembodiments, be a patterning material or a mask material. The patterningmaterial may be applied in any convenient fashion, such as by spincoating, die coating, or extrusion coating of a liquid, spraying on, orvapor depositing. The patterning material is generally applied to form asmooth layer with a patterned interface contacting the patternedtemplate 106. The smooth surface of the patterning material is thenapplied to a substrate using a technique similar to that used to detachthe template from the master substrate. Because the contacting surfaceof the carrier is curved, the template attached thereto, and thepatterning material applied thereon, acquires the curvature of thecontact surface of the carrier.

FIG. 1E is a side view illustrating the carrier 108 with the template106 and patterning material 114 as the patterning material 114 is beingapplied to the substrate 112. The smooth surface 120 of the patterningmaterial 114 is applied to the substrate 112 by contacting a first edge122 of the patterning material 114 to a first edge 128 of the substrate112, detaching the first edge 116 of the template from the carrier 108,attaching the first edge 116 of the template 106, or the first edge 122of the patterning material 114, to the substrate 112, or to a support(not shown) holding the substrate 112. As shown in FIG. 1F, the carrier108 is then rocked across the substrate 112 to contact a second edge 124of the patterning material 114 to a second edge 126 of the substrate112, detaching the second edge 118 of the template 106 from the carrier108, and attaching the second edge 118 of the template 106, or thesecond edge 124 of the patterning material 114, to the second edge 126of the substrate 112, or to a support (not shown) holding the substrate112. In some embodiments, the patterning material 114 may be partiallyor fully cured or dried prior to, and/or after, transfer to thesubstrate 112.

FIG. 1G is a side view illustrating a substrate 112 with a patterningmaterial layer 114 applied thereto, and a patterning template 106. In anembodiment wherein the template 106 is formed from a material withdifferent solubility from the patterning material 114, the template 106may be removed by dissolving to leave the patterning material layer 114,as shown in FIG. 1H. If the template material 106 is formed from PVA, asdescribed above, it may be readily dissolved by water. If the templatematerial 106 is formed from a hydrocarbon-soluble material, ahydrocarbon wash may remove it. In some embodiments, the substrate maybe dipped in a solvent bath. In other embodiments, the solvent may beflowed across the substrate surface. In still other embodiments, thesubstrate surface may be placed in contact with a solvent bath withoutdipping the entire substrate. In still other embodiments, the dissolvingprocess may comprise combinations of these techniques.

In alternate embodiments, the template 106 may be formed from a materialhaving different chemistry from the patterning material 114 such thatthe template 106 has different etch characteristics or differentreactions with chemical vapor or plasma from the patterning material114. In an embodiment wherein the template 106 is formed from a materialhaving different etch characteristics from the patterning material 114,the template 106 may be selectively etched using a chemistry having etchselectivity for the template material over the patterning material. Inyet another embodiment, the template 106 may be formed from a materialhaving a different reactivity to a chemical vapor or plasma from thepatterning material 114, such that the template material may bechemically altered by exposure to such chemical vapor or plasma, andthen removed by dissolving in liquid or etching.

After removal of the template 106, the patterning material 114 may beremoved incrementally to expose portions of the substrate 112 beneaththe thinner portions of the patterning material 114 while leaving thoseportions of the substrate 112 beneath the thicker portions of thepatterning material 114 covered. The substrate 112 may then be subjectedto etching or any other process designed to change the properties of theexposed portions thereof, such that the pattern is transferred from themaster substrate 102 to the substrate 112. In some embodiments, thedifferent thicknesses of the patterning material may be used fordifferential masking without removing the patterning material andwithout exposing any portion of the substrate. The different thicknessesprovide different permeability to process conditions that may be used toprocess or pattern the substrate.

The patterning material 114 may be removed from the substrate 112 afterpatterning, or it may remain on the substrate 112 to become an integralpart of the eventual device. In embodiments wherein the patterningmaterial 114 is to remain on the substrate 112, the patterning materialmay be formed from a material that is useful as a functional part of theeventual device. In some embodiments, the patterning material 114 may bean optical material applied to a glass, quartz, or plastic substrate asa functional layer.

FIGS. 2A and 2B are detail side views illustrating attachment of theflexible template 106 to the template carrier 108 and to the substrate112 according to one embodiment. As shown in FIG. 2A, the mastersubstrate 102 has a landing zone 204 that extends beyond an edge of thecarrier 108. The template 106 is formed with an attachment portion 202by covering the master substrate 102, including the landing zone 204,with template material. When the template 106 is to be detached from themaster substrate 102 and attached to the carrier 108, the attachmentportion 202, which may be an attachment strip in some embodiments, orone or more attachment tabs in other embodiments, is adhered to anattachment zone 206 of the carrier 108. Attachment of the template 106to the carrier 108 may be accomplished by any convenient method, such asby applying an adhesive between the attachment portion 202 of thetemplate 106 and the attachment zone 206 of the carrier 108, or bydrying, curing, melting, chemical bonding, heating, or cooling thetemplate material while in contact with the attachment zone 206. Inother embodiments, attachment of the template 106 to the carrier 108 maybe accomplished by fastening the attachment portion 202 of the template106 to the attachment zone 206 of the carrier 108 using a fastener, suchas a clamp. In some embodiments, the attachment zone 206 of the carrier108 may feature a recessed portion mated with a ring fastener to holdthe attachment portion 202 of the template 106 securely to theattachment zone 206. In some embodiments, the attachment portion 202 ofthe template 106 may extend around the edge of the carrier 108 to reachand attach to the obverse side 110 of the carrier 108 opposite thecurved template contact surface.

The attachment and detachment operations generally happen at certainpoints of the pattern transfer process. In the embodiment of FIGS.1A-1H, an attachment operation as illustrated in FIG. 2A may take placewhen the carrier 108 contacts the template 106 at the first edge 116. Anattachment portion at the first edge 116 may be attached to theattachment zone of the carrier to facilitate release of the template 106from the master substrate 102. The second edge 118 of the template maylikewise be attached to the carrier in the configuration of FIG. 1D. Therespective edges of the template may likewise be detached from thecarrier, and either the template or the pattern material attached to thesubstrate or a substrate support in the configurations of FIGS. 1E and1F.

FIG. 2B illustrates how the template 106 may be attached to a substrate112 in conjunction with detaching from the carrier 108. When the carrier108 is positioned so that the template 106 with the patterning material114 applied thereto contacts the substrate 112 at the first edge 208,the attachment portion 202 of the template 106 is detached from thecarrier 108 and attached to the substrate 112. In some embodiments, theattachment portion 202 of the template 106 may extend beyond thesubstrate 112 and attach to a substrate support below, as shown in FIG.2C, or along one edge of, the substrate. In other embodiments, theattachment portion 202 of the template 106 may extend beyond the edge ofthe substrate 112 to the side of the substrate 112 opposite the sidecontacting the patterning material 114. In all these embodiments, thetemplate may be secured to the substrate 112 or the support on which itrests, by adhesive, fasteners, chemical bonding, melting, curing,drying, heating, or cooling as described above. When the template 106 issecured to the substrate 112, the carrier 108 may detach from thetemplate 106 by rocking across the template 106, creating the gapbetween the carrier 108 and the template 106 shown in FIG. 2B. Inanother embodiment shown in FIG. 2C, the substrate support 212 may havea landing zone 210 extending beyond one or more edges of the substrate112 to which the attachment portion 202 of the template 106 may adhere.

In some embodiments, attachment and detachment of the template from themaster substrate and template carrier may be facilitated by surfacemodifications of the template, template carrier, master substrate,patterning material, substrate, or any of the above. In one embodiment,creating texture on the surface of the template that contacts thecarrier may facilitate detachment of the template from the carrier atthe appropriate time. Such texture may be created by abrading, scoring,or otherwise mechanically altering the surface, or by applying achemical release agent to the surface. If a release agent is to be used,it may be helpful to use a release agent with similar solubility to thatof the template. For example, if the template is water soluble, a watersoluble release agent, such as a fatty acid material, or a soap powder,may be useful. In some embodiments, the contact surface of the carriermay also be altered to facilitate adhesion or release. For example, acoating may be added to the master substrate surface, carrier contactsurface, substrate contact surface, substrate support surface, or any orall of them to promote adhesion or release, depending on the embodiment.In some instances, one or more of those surfaces may feature openingsthrough which vacuum or pressure may be applied to promote adhesion orrelease. In some embodiments, the template material may include amagnetic material that can be magnetically coupled to a carrier havingmagnetic properties to promote adhesion. The carrier may have transientmagnetic properties, such as through a powered magnetic assembly, forpromoting adhesion or release at appointed times. For example, amagnetic assembly may be powered with an attractive polarity to promoteadhesion of a magnetic template, and then powered with a repulsivepolarity to promote release. In another example, the master substrate,template carrier, substrate, or substrate support may be electricallybiased to promote a transient electrostatic adhesion. In otherembodiments, the reversible attachment and detachment means describedabove may also be applied to the landing zones and attachment zonesdescribed in connection with FIGS. 2A-2C.

In one embodiment, electrostatic means are used to hold the templatesecurely against the carrier and/or the substrate support. The templatecarrier may be configured with one or more bias members, such as aconductive template contact surface coated with a dielectric material ora conductive bias member embedded in the carrier. The one or more biasmembers may be coupled to one or more power sources for applyingelectrical bias to the template carrier. In operation, power is appliedto the template carrier when it contacts one edge of the template, andthe electrostatic force generated on the template adheres the templateto the carrier and detaches it from the master substrate as the carrierrolls across the template. In some embodiments, one or more bias membersmay have sections separated by insulators to allow individual sectionsof the carrier to be powered independently. This may facilitate carrierloading and unloading in ways described herein. In particular, atemplate adhered to a sectional electrostatic carrier may be applied toa substrate by contacting one edge of the template to the substrate andsuccessively de-energizing sections of the carrier as the carrier rollsacross the substrate. As sections of the carrier are de-energized, thetemplate detaches from the carrier and lays on the substrate. FIG. 4C isa schematic cross-sectional view of a template carrier 440 according toan embodiment. The template carrier 440 has a template contactingsurface 442 and a bias member 444 disposed in the carrier 440. The biasmember 444 of FIG. 4C comprises conductive sections 444A separated byinsulating spacers 444B to allow the bias member 444 to be powered bysection. In this way, electrical bias may be established in parts of thecarrier to facilitate attachment and detachment of a template thereto.In some embodiments, electrical bias may be reversed by section tofacilitate attachment of the template at one portion of the carrier anddetachment at another portion.

Electrostatic means may also be used to adhere the template to thesubstrate or substrate support. The embodiment of FIG. 2C illustrates asubstrate support 212 configured to apply electrostatic force. One ormore bias members 214 may be disposed in the substrate support 212 togenerate electrical bias to adhere the substrate and template to thesubstrate support. As described above, the one or more bias members 214may be sectional to allow partial biasing. In one aspect, the biasmember 214 may be powered to hold the substrate 112 and the template 106securely against the substrate support 212 by electrostatic force. Asthe carrier 108 releases the template 106, and the template 106 ispositioned proximate the substrate support 212, the bias adheres thetemplate 106 to at least the landing zone 210 by electrostatic force. Insome embodiments, the bias may apply substantial electrostatic force toall locations of the template, not just the attachment portion 202.

Embodiments described herein provide a method of patterning a substrate,comprising forming a template having a pattern to be applied to thesubstrate, attaching the template to a carrier having a curved surface,coating the template with a patterning material, applying the coatedtemplate to the substrate and detaching the coated template from thecarrier, and dissolving the template. The template is generally formedby solidifying a liquid precursor applied to the patterned surface of amaster substrate, such that the solidified template acquires the patternof the master substrate. In some embodiments, the template is attachedto the carrier by attaching the template to a first edge of the carrierand then attaching the template to a second edge of the carrier. Afterattaching the template to the first edge of the carrier, the carrier isrocked across the template until the second edge of the carrier contactsthe template. The template is coated with a patterning material, whichmay be a resist, and the coated template is applied to a substrate to bepatterned. A first edge of the coated template is placed in contact withthe substrate, and the template is detached from the carrier andattached to the substrate or substrate support. The carrier is rockedacross the substrate until a second edge of the coated template contactsthe substrate, after which the template is detached from the carrier andattached to the substrate support. The template is then dissolved,leaving the patterning material coating the substrate. The patterningmaterial can then be used to pattern the substrate.

The template is generally formed by solidifying a liquid precursorapplied to the patterned surface of a master substrate. The mastersubstrate may be made of any durable material, such as a glass or ametal, and may be patterned by any high-resolution patterning process,such as an e-beam process. The template precursor liquid may be acurable liquid, such as a liquid that solidifies upon drying or exposureto heat, light, or radiation. In one embodiment, PVA may be used as thetemplate precursor. In another embodiment, a polymer may be applied in aliquid or emulsified state. The liquid may be cured by drying orexposure to heat or light. In the case of PVA, drying causes the liquidto solidify into a flexible solid template. In the case of a polymer,drying may solidify the polymer by evaporating solvent, or applying heatmay cause a curing chemical reaction, such as cross-linking of polymerchains, to form a flexible solid. The solid template bears the patternof the master substrate by virtue of the liquid having flowed into thepattern recesses formed in the master substrate prior to solidifying.The liquid template precursor may be applied to the master substrate byspin coating (i.e. spinning the master substrate while pouring theliquid onto the master substrate), by die coating (i.e. dispensing theliquid precursor through an elongated die having a length approximatelythe same as one dimension of the master substrate as the die traversesthe master substrate), by extrusion coating (i.e. die coating whereinthe master substrate moves beneath the extrusion die), or by vapordeposition such as chemical vapor deposition (CVD, PECVD, MOCVD), atomiclayer deposition, or physical vapor deposition. In general, the templateprecursor liquid fills the pattern recesses of the master substrate andforms a smooth flat coating over the master substrate.

In many embodiments, the curable liquid template precursor is applied toa landing zone surrounding the patterned area of the master substrate.When the template is cured, the portion applied to the landing zonebecomes an attachment portion of the template. The attachment portionmay be useful in facilitating attachment of the template to the carrierand to the substrate support. For example, if the attachment portion ofthe template is a strip around the circumference of the template, thestrip may be adhered to the carrier head using adhesive or by using afastener. The strip may be inserted, for example, beneath a clamp on thecarrier or on the substrate support to attach the template to either. Inother embodiments, the attachment portion may be one or more tabs thatmay be attached by adhesive or clamping in a similar manner.

The template is detached from the master substrate by attaching it tothe carrier, and then using the carrier to incrementally detach thetemplate from the master substrate by applying a substantiallyunidimensional force to the template. In one embodiment, the carrier isplaced into contact with the template at a first edge. The template isdetached from the master substrate and attached to the carrier at thefirst edge. If the template has an attachment portion, as describedabove, the attachment portion may be detached from the master substrateand attached to the carrier. In some embodiments, the carrier may havean attachment zone on an edge thereof, or on the side of the carrieropposite the surface that contacts the template. Attachment of thetemplate to the carrier may be accomplished using adhesive or byclamping.

The surface of the carrier that contacts the template will usually becurved to facilitate application of the unidimensional separating force.The curvature may be uniaxial or multiaxial. In some embodiments, acarrier surface with uniaxial curvature may be most useful. In otherembodiments, a carrier surface with spherical or conical curvature maybe useful. The carrier contact surface is placed into contact with thetemplate at a first edge, and the template attached to the carrier. Thecarrier is then rocked or rolled across the template. As the carrierrolls across the template, the carrier applies a separating force to thetemplate, which separates from the master substrate without damage ordistortion. The separating force applied by the carrier is generallyfree of any shear which might distort the pattern formed in thetemplate.

The curvature of the template contacting surface of the carrier isgenerally slight. For most applications, if the carrier rests on a flatsurface, contacting the surface at its center point, a gap between theedges of the carrier and the flat surface of about 1 mm. or less willserve to manipulate the template. In many embodiments, the radius ofcurvature may be about 1,000 times the dimension of the carrier surfacethat has the contour. For example, a square carrier 1 meter on a sidemay have a radius of curvature of at least 1,000 meters. In someembodiments, a radius of curvature of the template contacting surfacemay compare to a major dimension of the carrier in a ratio of at leastabout 1,000:1, such as a ratio of at least about 1,500:1, for example aratio of at least about 2,000:1.

Rocking the carrier across the template comprises rotating the carrieraround an axis of rotation. In the case of a rectangular carrierattaching to a rectangular template, the carrier is rotated about anaxis perpendicular to the direction of “peel”. For example, if thetemplate is to be detached from the master substrate progressively froma first edge to a second edge, the carrier is attached to the templateat the first edge and rotated about an axis perpendicular to a linedrawn between mid-points of the first and second edges. As the carrierrocks across the template, a line of contact traverses across thetemplate contact surface of the carrier. As the line of contact passes apoint on the template, the carrier begins pulling away from the mastersubstrate, exerting a separating force tending to pull the template awayfrom the master substrate. The rocking motion of the carrier iscalibrated to translate the carrier in a direction perpendicular to theaxis of rotation. For example, the carrier may be translated whilerocking such that the center of rotation translates with the line ofcontact.

If the curvature of the carrier surface contacting the template issmooth, each point on the carrier surface follows a generally cycloidalpath near the template surface, approximating the shape of a cycloidnear a cusp. Each point may therefore be thought of as moving in adirection substantially perpendicular to the template surface contactingthe carrier surface. This motion generates a pulling force on thetemplate that is also substantially perpendicular to the templatesurface contacting the carrier, and substantially perpendicular to theplane described by the surface of the master template, which may bethought of as “horizontal”. As such, this pulling force is substantiallyunidimensional and perpendicular to the plane of the master template.The force is primarily tensile in character, pulling the template awayfrom the master substrate, but local shear forces may be realized inareas where the template is detached from pattern features having aprofile that is vertical or that departs appreciably from thehorizontal. Because the pulling force applied to the template issubstantially perpendicular to the “horizontal” plane of the mastersubstrate, compensation can be engineered for any distortion of thetemplate pattern introduced by detaching from the master substrate.

In embodiments featuring a template separation process wherein thecarrier rocks from a first edge to a second edge of the template, whenthe second edge of the carrier contacts the second edge of the template,the second edge of the template is detached from the master substrateand attached to the carrier by virtue of the attachment portiondescribed above. In some embodiments, it may be useful to attach thetemplate to the carrier around its entire circumference to minimize anytendency to sag or droop, thereby minimizing potential patterndistortions as the template is manipulated. In some embodiments,attachment of the template to the carrier may be enhanced by use ofadhesive or by vacuum. In other embodiments, it may be useful to endowthe template with magnetic properties, for example by embedding magneticmaterial in the template, and adhere the template to the carrier byapplication of magnetic force.

In some embodiments, the template attached to the carrier head is usedto transfer a pattern to the final substrate. In other embodiments, thetemplate may be used to imprint a pattern onto the substrate. Forexample, a patterning material may be applied to the substrate and thetemplate applied to the patterning material to form a pattern. In otherembodiments, a patterning material may be applied to the template andthe coated template applied to the substrate. In either case, thepatterning material will have some resistance to the process orprocesses to be used to pattern the substrate. The patterning materialwill generally be applied as a liquid, spin coated, die coated,extrusion coated, or sprayed onto either the template or the substrate,or as a vapor, deposited onto either the template or the substrate in avapor deposition process, and may be partially or completely cured ordried before, during, and/or after application of the template to thesubstrate. When applied to the template, the patterning materialacquires the pattern of the template by filling the pattern recesses inthe template and forming a smooth surface covering the template. Whenapplied to the substrate, the patterning material will acquire thepattern of the template as the template is contacted with the patterningmaterial, the patterning material flowing under pressure of the contactforce to fill the pattern recesses. If the patterning material is aviscous liquid, the contact force required to fill the pattern recesseswill be greater than when the patterning material is a non-viscousliquid. In one embodiment, the patterning material may be a non-viscousliquid that is cured after the pattern template is applied to thepatterning material. In either case, the template and patterningmaterial are eventually applied to the substrate.

The template, coated or uncoated, is generally applied to the substrate,or the resist-coated substrate, by a process similar to that used todetach it from the master substrate. The template, coated or uncoated,follows the curvature of the template contact surface of the carrier.Thus, the template may be detached from the carrier and attached to thesubstrate by contacting the template to the substrate at a first edge,detaching the first edge of the template from the first edge of thecarrier and attaching it to the first edge of the substrate or thesubstrate support, rocking the carrier across the substrate until thesecond edge of the template contacts the second edge of the substrate,detaching the second edge of the template from the second edge of thecarrier and attaching it to the second edge of the substrate orsubstrate support. In many instances, precise alignment of the templateon the substrate may be achieved through use of alignment processesknown to the art.

In some embodiments, it may be useful to facilitate adhesion and/orrelease of the template from the carrier through surface modification.To promote adhesion, an adhesive may be applied to the template or thetemplate contact surface of the carrier, or materials may be selectedfor construction of either to promote adhesion. To promote release ofthe template from the carrier, the surface of the template may beroughened by abrasion or scoring, or the template contact surface of thecarrier may be roughened through abrasion or scoring, or duringmanufacture. Additionally, a release agent such as a powder or chemicalmay be coated onto the template, the template contact surface of thecarrier, or both. A release agent will usually have solubility similarto that of the template. For example, if the template is water soluble,the release agent will generally also be water soluble, such as a fattyacid or soap powder, to facilitate complete removal with the template.

In some embodiments, one or more forces may be applied to aid inattaching the template to the carrier and detaching it from the carrier.A force delivery member may be included in any of the template carrier,the master substrate, or the substrate support to facilitate applyingforces to the template for attaching and detaching. In one embodiment,the force delivery member comprises a pneumatic member. Openings may beprovided in the template contact surface of the carrier, for example, toapply vacuum to the back side of the template to promote adhesion. Inanother embodiment, the template contact surface may comprise a porous,microporous, or nanoporous material capable of transmitting positive ornegative pressure (e.g. vacuum). In lithographic processes featuringvery small features, a nanoporous template contact surface may minimizestress concentration points capable of distorting the template patternwhen pressure or vacuum is applied. In another embodiment, if thetemplate is constructed of a magnetic material, the template carrier maycomprise a magnetic member, such that a magnetic field may be applied toadhere the template to the carrier. In another embodiment, an electricalbias generating member may be included in the template carrier togenerate an electrostatic adhesion force on the template. In each case,the adhesion force may be converted into a repulsive force by reversingthe action thereof. Pressure may be applied to detach the template fromthe pneumatic carrier, the polarity of the magnetic carrier may bereversed, or the polarity of the electrostatic bias or magnetic fieldmay be reversed, respectively. Also, in each case, the force deliverymember described may be included with the master substrate, thesubstrate being processed (e.g. a conductive member disposed in thesubstrate with exposed contacts for providing electrical bias to thesubstrate), and/or the substrate support in addition to, or instead of,the template carrier. It should also be noted that electrical bias maybe imparted to an electrically insulating template merely by impartingan electric charge to the dielectric material of the template.

Some alternative embodiments of carriers are illustrated in FIGS. 4A and4B. FIG. 4A is a side view of a carrier 400 having a first major surface404 and a second major surface 414. The second major surface 414 is alsoa template contact surface, and is curved with a radius of curvature atleast about 1,000 times the width w of the second major surface 414. Inthe embodiment of FIG. 4A, the first major surface 404 is also curved,and may have the same radius of curvature as the second major surface,or a different radius of curvature, either more or less than that of thesecond major surface 414. The carrier 400 has a thickness t, which maybe constant throughout the carrier. It should be noted that the curvedfirst and second major surfaces 404 and 414 may be circular (i.e. arcsof circles) or non-circular. For embodiments in which either the firstor second major surfaces are curved with non-circular shape, thethickness t may vary at different points along either surface. In suchembodiments, the second major surface 414, forming the template contactsurface, may have an average radius of curvature at least about 1,000times the width w of the second major surface 414, such as at leastabout 1,500 times the width w, for example at least about 2,000 timesthe width w. That is to say that the ratio of the average radius ofcurvature of the second major surface 414 to the width w of the secondmajor surface 414 may be at least about 1,000:1, such as at least about1,500:1, for example at least about 2,000:1.

The carrier of FIG. 4A has an exemplary support 412 located near acenter of the carrier 400. Any convenient support may be used, however,including swivel or rotatable mountings such that the carrier head maymove with respect to the support to perform the rocking action forattaching and detaching templates. The carrier 400 has edge portions 402that may be angled in some embodiments. The edge portions 402 may forman angle α with respect to the first major surface 404, for example,which may be constant at all locations along the periphery of thecarrier, or may vary in any desired way. In some embodiments, the edgeportions 402 may have a curved profile, if desired. Shaping and anglingof the edge portions 402 may be useful in some embodiments to promoteadhesion of the attachment portion of the template. In embodimentswherein the edge portion 402 is angled with respect to either the firstor second major surfaces 404, 414, the angle may range from near 0°,such as about 5°, to near 180°, such as about 175°. In some embodiments,the angle α will range between about 80° and about 100°.

FIG. 4B is a detail side view of another exemplary carrier 420configured to apply vacuum or pressure to promote adhesion and releaseof a template. The carrier 420 has an internal cavity 410 in fluidcommunication with conduits 408. The embodiment of FIG. 4B has twoconduits 408, but any convenient number may be used. The conduits 408are connected to a gas supply (not shown) for applying pressure, and toa vacuum source (not shown) for applying vacuum, with appropriate pipingand valves. The second major surface 414 of the carrier 420 has openings406 that allow transmission of pressure or vacuum to the interfacebetween the second major surface 414 and a template adjacent thereto(not shown). In an alternate embodiment, the second major surface 414has no openings, but is flexible, able to change shape throughapplication of pressure or vacuum to the internal cavity 410. Dividers416 may be disposed in the internal cavity 410 of the carrier 420 tocreate individual chambers. The individual chambers may be independentlypressured or evacuated to adhere or repel the template at the contactsurface 414 to facilitate loading and unloading of the carrier 420. Inone embodiment, dividers are disposed such that each chambercommunicates with only one opening 406. In another embodiment, dividersare disposed such that each chamber communicates with more than oneopening.

In still other embodiments, the carrier may be configured as acylinder-like object with an average radius of curvature large enough topreserve the substantially unidimensional character of forces applied tothe template. In such an embodiment, the ratio of the average radius ofcurvature of the portion of the cylinder-like object that contacts thetemplate to a major dimension of the template will generally be at leastabout 1:1 to apply substantially unidimensional forces to the template.

In many embodiments, the materials of the master substrate, carrier, andfinal substrate will be substantially matched to avoid distortions dueto temperature. If, for example, the carrier has significantly differentcoefficient of thermal expansion from the master substrate or the finalsubstrate, and if the temperatures of the two are significantlydifferent, the carrier may expand or contract during or after attachingthe template, creating a thermal distortion of the pattern. Matching thethermal properties of the substrates and carriers, and matchingtemperatures of the various steps and components of the apparatus,minimizes the chance of thermal distortion during patterning.

FIGS. 3A and 3B show a side view and top view, respectively, of anapparatus for processing substrates according to an embodiment of theinvention. In FIGS. 3A and 3B, a single master substrate 102 is engagedby two carriers 108A and 108B to pattern substrates 112A and 112B onsupports 302A and 302B, respectively. As can be seen in FIG. 3A, a firstcarrier 108A may be detaching a first template 106A from the mastersubstrate 102 in preparation for attaching the first template 106A to afirst substrate 112A to pattern the first substrate 112A, while a secondcarrier 108B is using a second, coated, template 106B attached theretoto pattern a second substrate 112B. After the first carrier 108A hasdetached the first template 106A from the master substrate 102, a newtemplate may be formed on the master substrate 102, and attached tocarrier 108B after carrier 108B detaches from the second template 106B.In this way, a single master substrate 102 can be used to patternmultiple substrates efficiently. Patterning material may be applied tothe templates 106A and 106B by a coating station (not shown in FIG. 3A)that utilizes any convenient technique, such as spraying, spin coating,ribbon coating, dipping (with or without rocking), and the like.

The embodiment of FIG. 3B illustrates that the substrate supports 302Aand 302B may be moving supports that carry successive substrates topatterning stations adjacent to the carriers 108A and 108B. Also shownin the embodiment of FIG. 3B is an application station 304 forpatterning material. Either of the carriers 108A/B having attached atemplate formed using the master substrate 102 may move the template tothe application station 304 to receive patterning material.

In some embodiments, a single master substrate may operate with a firstplurality of carriers and a second plurality of patterning lines orstations by disposing successive substrates in each patterning station.In some embodiments, the first plurality may be equal in number, or lessthan, the second plurality. In some embodiments, a single mastersubstrate may be used with one or two carriers and two patterningstations. In other embodiments, a single master substrate may be usedwith one, two, or three carriers and three patterning stations. In otherembodiments, a first plurality of master substrates, a second pluralityof carriers, and a third plurality of patterning stations may be usedtogether, with the first, second, and third pluralities being the sameor different in number. Each master substrate of the first plurality mayhave the same pattern, or a different pattern, formed therein. Forexample, a first master substrate may be used to transfer a firstpattern to a substrate, and then a second master substrate may be usedto transfer a second pattern to the same substrate. In some embodiments,a plurality of master substrates may be used to transfer a plurality ofsuccessive patterns to a single substrate.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof.

1. An apparatus for patterning a substrate, comprising: a mastersubstrate; a substrate support; and a template carrier movable betweenthe master substrate and the substrate support, wherein the templatecarrier comprises a curved template contact surface having a width and aradius of curvature, wherein a ratio of the radius of curvature to thewidth of the contact surface is at least about 10:1.
 2. The apparatus ofclaim 1, wherein the substrate support comprises a landing zone forholding a template securely against the substrate support.
 3. Theapparatus of claim 1, wherein the curvature of the template contactsurface has one axis.
 4. The apparatus of claim 1, wherein the templatecarrier comprises an attachment zone configured to hold the templatesecurely against the template carrier.
 5. The apparatus of claim 1,wherein at least one of the template carrier, the master substrate, andthe substrate support comprises a force delivery member.
 6. Theapparatus of claim 5, wherein the force delivery member comprises anelectrical bias generating member.
 7. The apparatus of claim 5, whereinthe force delivery member comprises a pneumatic member.
 8. The apparatusof claim 2, wherein the master substrate comprises a landing zone forforming an attachment portion of a template.
 9. The apparatus of claim1, wherein the template carrier has a curved surface with more than oneaxis of curvature, and the template carrier comprises a pneumatic forcedelivery member.
 10. An apparatus for creating a pattern on a substrate,comprising: a substrate support comprising a landing zone for holding acured template securely against the substrate support; a source ofcurable template material positioned to deliver curable templatematerial to a master substrate; and a plate-like template carrier withone surface that has a slight curvature, wherein the plate-like templatecarrier receives a cured template from the master substrate.
 11. Theapparatus of claim 10, wherein the template carrier is movable betweenthe substrate support and the master substrate.
 12. The apparatus ofclaim 10, wherein the template carrier comprises a template fastener.13. The apparatus of claim 12, wherein the template fastener is a ringfastener.
 14. The apparatus of claim 13, wherein the template carrierfurther comprises a recess that mates with the ring fastener.
 15. Theapparatus of claim 14, wherein the surface of the plate-like templatecarrier has a width and a radius of curvature, and a ratio of the radiusof curvature to the width is at least about 10:1.
 16. An apparatus forpatterning a substrate, comprising: two or more substrate supports; anda plate-like template carrier movable among the two or more substratesupports, the template carrier having a mechanical template fastener anda curved template contact surface that is roughened.
 17. The apparatusof claim 16, wherein at least one of the template carrier and thesubstrate support comprises a force delivery member.
 18. The apparatusof claim 17, wherein the force delivery member comprises an electricalbias generating member.
 19. The apparatus of claim 17, wherein the forcedelivery member comprises a pneumatic member.